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Hello everybody. I just finished putting back together my 87 944S after getting the head resurfaced and a valve job and the car will start sometimes and sometimes it will not. Currently it falls under the it will not. I have replaced tons of parts on the car including speed/reference sensor, fuel pump, fuel filter, every gasket from the head gasket up, spark plugs, spark plug wires, all belts, new vacuum lines, I had the fuel injectors rebuilt, new fuel lines, and some other things. When I got the car and it would run on starting fluid then cut off. I set the ignition timing off the workshop manual so i’ve checked that off the list of things that it could be. The spark plugs are wet with fuel when I take them out. I have voltage at the ignition coil. I have great compression on all cylinders. When the car does start sometimes the idle is at 1k rpm sometimes at 1100 rpm and sometimes at 900. The car will crank but not fire. Any ideas of what my issue could be? Thanks in advance to those that respond.
Last edited by Bryant1234; 02-15-2023 at 12:09 AM.
It could be the FPR leaking fuel into the vacuum line, that can be checked carefully but be mindful of starting a fire. I would suggest using a DME Relay jumper to run the fuel pump with the engine off and have a container ready to catch fuel from the FPR vacuum port rather than cranking and making sparks.
Test the spark with a spark checker to see if it is adequate. You can also rig something up to see if the spark will jump maybe 20mm and it should be bright blue-white, not orange. However a spark checker is better.
Coils rarely go bad but The S and S2 cars have an ignition module that can also fail.
By "ignition timing" I assume you mean valve timing?
16v cars can also have alignment issues with the distributor housing that can damage the cap and rotor.
If it's over-fueling and not the FPR or the temp sensor the injectors might not be OK despite the rebuild, you could try pulling the connector on one to see if that helps. One could be hosing or dripping.
Yes I meant valve timing sorry. I checked for fuel on the vacuum side and none came out. I did check for spark and it turns out I have none. I tested the ignition coil and it works. I'm thinking it might be the cap or rotor like you said. Would you happen to know how to determine which one it is. Id love to buy a new one of but this car has already put me on the verge of chapter 11.
Yes I meant valve timing sorry. I checked for fuel on the vacuum side and none came out. I did check for spark and it turns out I have none. I tested the ignition coil and it works. I'm thinking it might be the cap or rotor like you said. Would you happen to know how to determine which one it is. Id love to buy a new one of but this car has already put me on the verge of chapter 11.
You say you tested the ignition coil, but does that mean you checked the primary and secondary coil resistance? Have you checked that you are getting running signals (speed/ref sensors)/secondary voltage to ignition coil? One way to check is to see if you have tach bounce while cranking. http://www.clarks-garage.com/shop-manual/ign-04.htm
I would do this before moving on to cap and rotor (although those replacements are rather cheap so if they look worn it may be best to replace anyways). Typically you will see wear/carbon on the electrodes inside the cap and on the rotor, so much that it either creates too much gap to make a connection or has so much carbon that it blocks a connection.
Also the 16v cars have an external ignition control module/igniter, something the 8V cars dont have (I think its internal in the DME). This should also be checked. Its located in the drivers side headlight bucket area.
Last edited by walfreyydo; 02-15-2023 at 03:52 PM.
I did the ignition coil test above the resistance test on the clark's garage page but my ohmmeter battery is dead so I'm going to get a new one to do the secondary test. I just replaced the speed/reference sensor and it came with a gapping tool that I used to set it up correctly. My tachometer is also bouncing as I try to start. It's close to 180 bucks for both the parts so just trying to minimize cost. I took the cap and rotor off and do not see any build up and no cracks but I do see where it looks like whatever material that was used on the top of the rotor has started running down the side of it. Here is a picture for reference.
The rotor looks ok. Tach bounce I think you can assume speed/ref sensor (running signals) are working. I would run the primary/secondary resistance checks if you can and then test for voltage at the distributor to see if the coil is sending power. Also look into testing that ignition control module.
Also, when the car wont start for you, try jumpering the DME relay and see if that makes any difference. I posted the link on how to do this above. The reason is the DME relay sends power to the fuel pump, DME and injectors, so if the relay is acting up intermittently this could cause no start issues caused by lack of fuel - as you describe (ie: running on starting fluid only).
In your first post you said it runs on starting fluid.. that means you have spark, but no fuel. But further down your post you say you dont have spark and the spark plugs are full of fuel, which seems to contradict the first part. Im a bit confused. Not sure if we are dealing with an intermittent spark issue or intermittent fuel issue (DME relay). I think we really need to do some further testing to nail down whether this is fuel or spark related...
Im still leaning towards DME relay as this is the most common issue of a no start condition. Jumper it and report back.
Last edited by walfreyydo; 02-15-2023 at 04:13 PM.
I took the dme out of a running car and tried it and no change but thank you for the recommendation.
Im trying to find a way to test the ignition control module but cant find much on it.
Sorry to confuse you about the spark/fuel issue. When I first got the car it would run on starting fluid as I said but then it would shorty cut off. I replaced the fuel pump which is what I thought the issue was when I first got the car but in the midst of everything I did the head gasket because I was already replacing the timing chain and tensioner pads. It now seems that I do have a spark issue even though I didn't have one when I got the car and Im not sure why. When I take the plugs out they are wet on the end and I can also hear the fuel pump running and I can hear the fuel flow through the lines and into the rail. I tested the plugs by pulling the spark plug wire out the spark plug hole and attaching a spark plug to the end of the plug wire and I also attached a ground to the plug. I did the same test on an 8 valve 944 beside me and the plugs sparked, but I do the same test on the 16 valve and nothing.
Last edited by Bryant1234; 02-15-2023 at 04:21 PM.
Turns out the coil is getting power but its not sending spark to the distributor. I took the wire for the coil out of the distributor and connected a spark plug to the end of the coil wire and also connected a ground to the spark plug and no spark is coming out as I crank and again I did the exact same test on another car and spark was coming out the plug.
In addition to the test above, you may elect to perform an ignition coil resistance check as confirmation of the coil's condition.
Check the ignition coil primary coil resistance by connecting an ohmmeter between the positive (Black wire) and negative (Green wire) terminals on the coil. The resistance should be 0.4 to 0.6 ohms.
Check the ignition coil secondary coil resistance by connecting an ohmmeter between the coil output terminal and the ignition coil negative terminal. The resistance should be 5000 to 7200 ohms.
You will also want to look at testing the ignition control module
Last edited by walfreyydo; 02-15-2023 at 05:53 PM.
The car is still idling at 1000 rpm so now I'm trying to figure that out
Are you getting that number from the cars tach or another source? I have two clusters for my car (late model) and both of them read about 300rpm higher at idle, catches up around 3000 then reads slower the rest of the way, getting worse the higher it gets. This is when I compare it to my EBC set to tach.
Im getting the rpms from the cars tachometer. I think its reading correctly because I can hear the difference in sound from 800 to 1000 rpm but can never be to sure until I check the rpms another way. My car also wants to stumble and die every time I stop when my car goes back to idle speed which is exciting but runs great when I am higher in the revs
02-14-2023, 09:54 PM
944S 16 valve intermittent starting issue, idle fluctuation
but runs great when I am higher in the revs